Kepler Finds 'Super-Earth' Exoplanet in First Discovery of New Mission

The Kepler space telescope has found its first new exoplanet, a “super-Earth,” of its secondary mission phase. The discovery adds to a current tally of 996 confirmed exoplanets and 4,183 planetary candidates already found by the revolutionary planet-hunting telescope.

The discovery not only adds to an ever-growing list of known worlds outside our Solar System, but also verifies that Kepler can continue to do amazing science in this new phase of the mission, known as K2, which was developed after problems with the telescope’s reaction wheels, which keep it stabilized enough to focus on its target stars, threatened to end the mission for good.

Three other known potentially habitable super-Earths, compared in size to the Earth. Image Credit: PHL @ UPR Arecibo/NASA

“Last summer, the possibility of a scientifically productive mission for Kepler after its reaction wheel failure in its extended mission was not part of the conversation,” said Paul Hertz, NASA’s astrophysics division director at the agency’s headquarters in Washington. “Today, thanks to an innovative idea and lots of hard work by the NASA and Ball Aerospace team, Kepler may well deliver the first candidates for follow-up study by the James Webb Space Telescope to characterize the atmospheres of distant worlds and search for signatures of life.”

The new exoplanet, called HIP 116454b, is 180 light-years away and 2.5 times the diameter of Earth and orbits very close to its star. Even though the star is smaller and cooler than our Sun, the planet’s tight orbit of only nine days means that it is far too hot for life as we know it.

Some super-Earths may be true water worlds, completely covered by oceans. Image Credit: JPL-Caltech/Ames/NASA/AP

The discovery was made during a study of data from a test of K2 in February 2014. It was later confirmed by measurements from the HARPS-North spectrograph of the Telescopio Nazionale Galileo in the Canary Islands.

The discovery proves that Kepler is still quite capable of finding yet more new exoplanets, despite the earlier mechnical problems. It also adds to the increasing number of super-Earth discoveries, unique exoplanets not found in our own Solar System.

“The Kepler mission showed us that planets larger in size than Earth and smaller than Neptune are common in the galaxy, yet they are absent in our solar system,” said Steve Howell, Kepler/K2 project scientist at NASA’s Ames Research Center in Moffett Field, Calif. “K2 is uniquely positioned to dramatically refine our understanding of these alien worlds and further define the boundary between rocky worlds like Earth and ice giants like Neptune.”

Illustration of Kepler during its new K2 mission. Image Credit: NASA Ames/JPL-Caltech/T Pyle

Kepler’s primary mission ended in May 2013 after the failure of the second of its four reaction wheels. With only two remaining working reaction wheels, Kepler was not able to maintain enough stability to continue its exoplanet observations. The mission seemed to be at an end until an ingenious solution was found: using the pressure from sunlight to act as a third “virtual reaction wheel.” It worked, and the K2 mission officially began in May 2014. To date, Kepler has already observed more than 35,000 stars and collected data on star clusters and dense star-forming regions, as well as several planetary objects within our own Solar System.

Another benefit of the K2 mission is that Kepler can now expand its search to bright nearby stars. Any exoplanets orbiting them could be studied in greater detail than ones found earlier by Kepler. The calculated density of an exoplanet can be used to determine if it is a rocky, watery, or gaseous world.

Some super-Earths are thought to be true water worlds, with their surfaces covered completely by oceans. Evidence also now suggests that they are one of the most common types of exoplanets, at least in our Galaxy.

According to John Johnson of the Harvard-Smithsonian Center for Astrophysics, “HIP 116454b will be a top target for telescopes on the ground and in space.”

The new research paper will be published in The Astrophysical Journal. More information about the Kepler mission is available here.